Gelling of hydrazine



3,164,505 GELLING OF HYDRAZINE I Paul Y. Hsieh and James V. CartmellyDayton, Ohio, assignors to The National Cash Register Company, Dayton, Ohio, a corporation of Maryland No Drawing. Filed Get. 25, 1962, Ser. No. 233,153

8 Claims. (Cl. 149-36) This invention relates to gelled fuel compositions and to a method for making such gels. More specifically, it

relates to a semi-rigid to rigid gelled fuel composition comprising a major proportion of substantially anhydrous hydrazine and a minor proportion of a fatty acid ester of a polyol as a gelling agent. v

Hydrazine is a well-known and commercially-available chemical compound and hasbeen widely used in both industry and research. For example, it is useful as an .intermediate in the manufacture of many industrially-important chemicalssuch as, for example, agricultural, textile, photographic, and other chemicals. Hydrazine is also important in the manufacture of explosives and-as an essential ingredient in many industriallydmportant processes. In addition to the above-mentioned uses for hydrazine, it; is a powerful and efiicie'nt fuel for rocketandjet engines. Because of its low molecular weight andhigh put per unit weight.

heat of combustion, hydrazine provides high energy out-.

tion is burned in air or in oxygen, it provides the same energy output per unit weight, obtained with 'normally liquid untreated hydrazine.- g

For reasons apparent to those skilled in the art, many advantages inhere in the use of solid, rigid, or semi-rigid fuels instead of liquid fuels for jetand rocket propulsion.

In accordance with the present invention, hydrazine, which normally is liquid at room temperature (having a melting point of 2 degrees centrigrade andaboiling point of 113 degrees Centigrade), is readily and efficiently converted to a self-supporting rigid or semi-rigid mass,'in;a form suitable for use as arocketfuel, by simply nnxing a minor amount of an ester or of esters of certainfatty acids and polyols, which are specified-hereinafter, with said hydrazine, and allowing the mixture to gel at room temperature, either with or without agitation.

Thus, a prime object of the invention is to provide a a polyol, the resulting composition having a greatly reduced hydrazine vapor pressure when compared to the vapor pressure of pure hydrazine.

These and other objects of the invention are achievedby a substantially anhydrous, self-supporting, gelled fuel composition comprising:

(l) A major amount of hydrazine, and.

(2) A minor amount of fatty acid ester from the group consisting of: q

tate ester of sorbitan, 2 I V (b) fatty acid esters of zapolyethylene Q selected from the group consisting dime monostearate and the dilaurate'ester' of polyethylene glycol, said polyethylene glycol being liquid at room. temperature and having f an average molecular weight rangefrom 200 to 600, and

(0) mixture" of fatty acid esters in (a) and (b').

- The following example demonstrates a preferred meth- 0d for preparing gelled hydrazine accordingto the invention:

drous hydrazine (95+%) maintained at room temperature in a suitable con-tainen the contents being stirred during the addition. The time required for adding thes'orbif two (2.) minutes, a rigid, well-set, non pourable gelv had formed. No change intempera-turewas noted during the I gelling operation.

The amount of ester' wliich may be used for:making the gelled hydrazine-composition is not critical so long as at least a minor amount of the ester'based'on the total weight of ester and hydrazineis present; however, amounts of ester up to ten (10) percent are preferred. Gelled hydrazine-ester compositions having optimum characterist-ics;;a re generally obtained with three (3) percent, by weight, Qf theiester. 1 f

- It has been found that the consistency ofthefgel, which may range from soft; and pourable to semi-rigid or rigid and non-pourable, isdirect-ly proportional tothe,ester concentration; x The higher the concentration, the more rigid the gel." However; for any given consistencyj: the gelling time required for th'ejgel to reach said consistency is a function of the specific este'randgto a lesser-extent from the following table g v Approximate'gelling time vs." Gelling Agent 1, concentration of ester'gelling. g

-' agentsv Percent Agent' l 1%, 3%

rsorbltan monooleate i Sorbltan dioleate 10 min 2 to 5 Soroitan trioleate utes min- Sorbitan mon0stearate utes Sorbitan monopa'lmitate' 1 n r v Polyethylene glycol monostearate Approximately one hour' at .Polyethylene glycol d1laurate 3% to 10% concentration 1 Compounds sold under the trademarlr"Span." 7

I Time required to reach maximum consistency.

on the total composition weight'unless otherwise indicated.

than with polyethylene glycol esters and that, for all practical purposes, when the latter is used'as gelling'agent, V "the rate of-gelling is substantially independentiof ester concentrationbetween 3 'percentand 10 percent ester.

selected from When a sorbitan ester is the gelling agent, anincrease or decrease in the concentration of said agent by afactor of ten decreases o'r-increases the gelling time ,to'maximum fconsistency by a factor of about l0, respectively. Hence,

the gellingrate is directly proportional to the concentrationin thera'ngel of 1 percent to 10 percent gelling agent: No satisfactory theory 'orfmechanism has been found a lj toexplain the instantly-described andp-claimed gelling a 3,164,505 Patenteddani 5, 19 65 7 Three (3) grams of sorbitan mono oleateISpan 8d) 7 was rapidly add'ed'to ninety-seven (97) grams of anhyaction, However, the action apparently is highly specific in nature, since, from among a large number of surfaceactive compounds tested, only the above-specified compounds were effective as gelling agents for hydrazine. Itwill be understood by those skilled in the art that hydrazine, as well as other solid and liquid rocket propellants, are customarily utilized with oxidizers. Thus, it should be apparent that the gelled hydrazine compositions of the invention may comprise, preferably in minor proportion, such conventional oxidizers as, for example, nitric acid, oxygen progenitors such as ammonium nitrate, potassium perchlorate, 1*etc., oxygen, and nitrogen tetroxide. Some fuel and oxidizer combinations are known to be hypergolic, and the two must, of necessity, be maintained out of contact with each other until it is desired to initiate the combustion. However, in fuel-and-oxidizer combinations which are not hypergolic, the oxidizer may be blended directly with the constituents for forming the gelled hydrazine composition.

In addition to providing hydrazine. in a semi-rigid or rigid form suitable for use as a jet and rocket fuel propellant, gelled hydrazine, as described herein, overcomes several recognized problems anddisadvantages associated with the storage, handling, and, shipping of the normallyliquid hydrazine. Since hydrazine vapor is highly toxic and corrosive, particularly to the eyes, and forms explosive mixtures with air, it has been customary in the past to store and ship hydrazine in strong metal or glass containers. Heretofore, it was not, feasible to use flexible and non-flexible polymeric, and other conventional packaging materials for the storage or shipment of hydrazine, because a numbereof such materials were reactive with hydrazine, while others were not sufiiciently impermeable to hydrazine,.in either liquid or vapor state, to provide a safe level of, protection. It has nowlbeen found that, at room temperature, gelled hydrazine compositions prepared according to .the inventionhave approximately one sixth-(V6) the hydrazine, vapor pressure of untreated hydrazine at the, same temperature. Because of this characteristic, gelled; hydrazine, of the invention can now be packaged, stored, and shipped in containers fabricated from-unreactive packagingtmaterials, such as flexible polymeric materialsand other conventional materials, as Well as in the metal and glass containers required in the past.

Although the invention is described above in terms of certain materials and embodiments, it should be understood that it issusceptible to changes without departing polyethylene glycol monostearate.

sorbitan dioleate.

' (l) A major amount of hydrazine, and

" (2) A minor amount of fatty acid ester selected from the group consisting of:

(a) fatty acid esters of sorbitan selected from the group consisting of the monooleate, dioleate, trioleate, monostearate, and monopalmitate ester of sorbitan, Y Q i (b) fatty acid esters of-polyethylene glycol selected from the group consisting of ;the monostearate and the dilaurate ester of polyethylene glycol, said polyethyleneglycol being liquid at room temperature and having an average molecular weight range from 200 to 600, and i (0) mixture of fatty 'acid esters in (a) and (b).

2.1The composition of claim 1 wherein said composition comprises: 7 a

(l) at least 90 percent, by weight, hydrazine, and (2) up to 10 percent, by weight, of the ester, the percentages basedon the total Weight of hydrazine and ester. 3. The composition sorbitan monooleate.

4. The composition of claim 1 wherein the ester is of claim 1 wherein the ester is 5. The composition of claim 11 wherein the ester is sorbitan trioleate. j a

6, The composition of claim 1v whereintheester is 7. The composition of claim 1 wherein comprises:

(1) 97 percent, by weight, hydrazine, and (2) 3 percent, by weight, of the ester, the percentages based on 'thetotalweight of hydrazine and ester. 8. The method of converting normally liquid substantiallyauhydrous hydrazine to a firm self-supporting gel which comprises dissolvin'gi'n said anhydrous hydrazine,-

said composition withlittleor no agitation, at" room temperature, a minor from the scope of the invention as described in the following claims:

What is claimed is:

1.-A substantially anhydrous, self-supporting, gelled fuel composition comprising: 7

References Cited in the filelof this patent -UNITED STATES PATENTS Griflin etal. .Feb. 20, 1962 Rice Feb. 12, 1963 

1. A SUBSTANTIALLY ANHYDROUS, SELF-SUPPORTING, GELLED FUEL COMPOSITION COMPRISING: (1) A MAJOR AMOUNT OF HYDRAZINE, AND (2) A MINOR AMOUNT OF FATTY ACID ESTER SELECTED FROM THE GROUP CONSISTING OF: (A) FATTY ACID ESTERS OF SORBITAN SELECTED FROM THE GROUP CONSISTING OF THE MONOOLEATE, DIOLEATE, TRIOLEATE, MONOSTEARATE, AND MONOPALMITATE ESTER OF SORBITAN, (B) FATTY ACID ESTERS OF POLYETHYLENE GLYCOL SELECTED FROM THE GROUP CONSISTING OF THE MONOSTEARATE AND THE DILAURATE ESTER OF POLYETHYLENE GLYCOL, SAID POLYETHYLENE GLYCOL BEING LIQUID AT ROOM TEMPERATURE AND HAVING AN AVERAGE MOLECULAR WEIGHT RANGE FROM 200 TO 600, AND (C) MIXTURE OF FATTY ACID ESTERS IN (A) AND (B). 